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x86/cpu: Fix up srso_safe_ret() and __x86_return_thunk()

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commit af023ef335f13c8b579298fc432daeef609a9e60 upstream.

  vmlinux.o: warning: objtool: srso_untrain_ret() falls through to next function __x86_return_skl()
  vmlinux.o: warning: objtool: __x86_return_thunk() falls through to next function __x86_return_skl()

This is because these functions (can) end with CALL, which objtool
does not consider a terminating instruction. Therefore, replace the
INT3 instruction (which is a non-fatal trap) with UD2 (which is a
fatal-trap).

This indicates execution will not continue past this point.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230814121148.637802730@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Zijlstra 2023-08-14 13:44:28 +02:00 committed by Greg Kroah-Hartman
parent 6e4dd7d263
commit 8bb1ed390d
1 changed files with 2 additions and 2 deletions
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4
arch/x86/lib/retpoline.S
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@ -202,7 +202,7 @@ SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
int3
lfence
call srso_safe_ret
int3
ud2
SYM_CODE_END(srso_safe_ret)
SYM_FUNC_END(srso_untrain_ret)
__EXPORT_THUNK(srso_untrain_ret)
@ -212,7 +212,7 @@ SYM_CODE_START(__x86_return_thunk)
ANNOTATE_NOENDBR
ALTERNATIVE_2 "jmp __ret", "call srso_safe_ret", X86_FEATURE_SRSO, \
"call srso_safe_ret_alias", X86_FEATURE_SRSO_ALIAS
int3
ud2
SYM_CODE_END(__x86_return_thunk)
EXPORT_SYMBOL(__x86_return_thunk)